permutation (n.)youdaoicibaDictYouDict[permutation 词源字典]
mid-14c., from Old French permutacion "change, shift" (14c.), from Latin permutationem (nominative permutatio) "a change, alteration, revolution," noun of action from past participle stem of permutare "change thoroughly, exchange," from per- "thoroughly" (see per) + mutare "to change" (see mutable).[permutation etymology, permutation origin, 英语词源]